Kinetic pathways of gyroid-to-cylinder transitions in diblock copolymers under external fields: cell dynamics simulation

Abstract

Using cell dynamics simulation we investigate the cubic gyroid morphology of block copolymer melts under simple shear flow and electric field. The electric field should be stronger than a certain critical value to induce transition to a cylindrical phase. In the case of simple steady shear the gyroid-to-cylinder transition was observed even for a very weak shear. Quantitative analysis of pathways of gyroid-to-cylinder transition is performed by means of Minkowski functionals. We found that the kinetics of the gyroid-to-cylinder transition are different under electric field and shear flow. Moreover, the gyroid structure under different strengths of electric field shows different pathways. Different types of intermediates such as five-, four-fold connections and "winding" cylinders are found for different pathways. This journal is © The Royal Society of Chemistry

Mechanisms of electric-field-induced alignment of block copolymer lamellae

“…The time evolution of the order parameter is given by the Cahn-Hilliard-Cook (or the time-dependent Ginzburg-Landau) equation, [10][11][12][13][14][15][16][17][18] which in the presence of an applied electric field (along the y direction) becomes:…”

“…We implement a Ginzburg-Landau approach in a cell dynamics simulation (CDS), which is a very fast computational technique [10][11][12][13][14][15][16][17][18] and can serve as a research precursor for more elaborate but slow methods like SCFT. For a symmetric AB diblock copolymer the structure can be described by an order parameter …”

“…17,19 The last term in eqn 1 was derived using the expression for the chemical potential 20 and expanding the dielectric constant 3 and Maxwell equation div(3E) ¼ 0 in the leading power of j. The dimensionless time is tM/a 0 2 , where the lattice cell size a 0 and M are set to 1.…”

Phase Coexistence in a Dynamic Phase Diagram

“…[37] Moreover,agyroid-to-cylinder transition is reported for diblock copolymers, [38] in which cylinders can be hexagonally packed. [39] As the existence and properties of equilibrium-phase coexistence is of interest, the focus of this paper is phase coexistence regions in the dynamic phase diagram and also the relative stabilityo ft he formed microstructure after the applied deformation.…”

Influence of substrate interaction and confinement on electric-field-induced transition in symmetric block-copolymer thin films

“…Dynamic density functional theory (DDFT) [27,28,30,31], self-consistent-field theory (SCFT) [25,29] and cell dynamics simulations (CDS) [32] have previously been employed to study electric field induced alignment.…”